(Useful information) : $\sqrt{167 R T}=640 j^{1 / 2} mole ^{-1 / 2} ; \sqrt{140 RT }=590 j ^{1 / 2} mole ^{-1 / 2}$. The molar masses $M$ in grams are given in the options. Take the value of $\sqrt{\frac{10}{ M }}$ for each gas as given there.)
(A) $M=20 \times 10^{-3} \quad f =320 Hz$ $\quad\quad$$\Delta f = \pm 4.5 Hz$ Not possible
(B) $M=20 \times 10^{-3} \quad f =253 Hz$ $\quad\quad$$\Delta f = \pm 3.6 Hz$ Not possible
(C) $M=32 \times 10^{-3} \quad f =237 Hz$ $\quad\quad$$\Delta f = \pm 3.4 Hz$ Not possible
(D) $M =36 \times 10^{-3}$ $\quad$$f =242.8 Hz$ $\quad\quad$$\Delta f = \pm 3.5 Hz$ possible
